1. Field of the Invention
The present invention relates to a process for enzymatically producing a dietary sterol fatty acid ester (i.e., a sterol fatty acid ester for food) from a vegetable oil deodorizer distillate using a lipolytic enzyme.
Particularly, the first aspect of the present invention relates to a process for enzymatically producing a physiologically active, inexpensive dietary sterol fatty acid ester from a vegetable oil deodorizer distillate using a lipolytic enzyme such as a lipase as a catalyst.
The second aspect of the present invention relates to a process for producing a dietary sterol fatty acid ester from a vegetable oil deodorizer distillate at low cost.
The third aspect of the present invention relates to a process for producing a dietary sterol fatty acid ester from a vegetable oil deodorizer distillate at low cost, more specifically a process for producing a dietary sterol fatty acid ester from a vegetable oil deodorizer distillate using a lipolytic enzyme capable of selectively esterifying cis fatty acids.
2. Description of the Related Art
In the purification processes for plant oils such as soybean oil and rapeseed oil, various sterols such as xcex2-sitosterol are usually produced as parts of unsaponifiable matters. Particularly xcex2-sitosterol is known to have an effect of reducing plasma cholesterol level in the body. It has recently become apparent that xcex2-sitostanol, a saturated form of xcex2-sitosterol, has a more potent effect of reducing plasma cholesterol level than xcex2-sitosterol and has been focused.
However, since the above-mentioned free sterols and free stanols are insoluble in the micellar phase in the digestive tract, they are not appropriate for intake to develop their physiological effects. In order to improve the fat-solubility thereof, it has been proposed to modify them in the form of a sterol fatty acid ester. In recent years, it has been attempted to add a sterol fatty acid ester into various food products such as margarine with vegetableterol.
A sterol fatty acid ester has currently been used mostly in a cholesteric liquid crystal and as a hydrophilic base material for pharmaceuticals and cosmetics. Such a sterol fatty acid ester has been produced by chemical synthesis with an acidic or basic catalyst. In chemical synthesis, however, the reaction should be conducted under extreme and severe conditions in most instances, and several problems may arise such as degraded quality of a product and generation of undesirable by-products. Consequently, it is unavoidable to employ highly complicated purification steps after the synthetic reaction. If contemplating the use in food products or pharmaceuticals, there will be a problem that they may be contaminated with by-products or reaction catalysts.
In order to avoid the disadvantages as mentioned above, use of an enzyme in the synthesis reaction has been studied.
Such an enzyme includes a cholesterol esterase and a lipase. Both types of enzymes are categorized as carboxylic acid ester hydrolase. A cholesterol esterase is defined as an enzyme which can break a cholesterol fatty acid ester into a free sterol and a free fatty acid through hydrolysis. A lipase, which usually means triacylglycerol lipase, is defined as an enzyme which can break a glycerol fatty acid ester into glycerol and free fatty acids through hydrolysis.
However, there are found many enzymes having both of cholesterol esterase activity and lipase activity (see D. Lombardo et al., Biochem. Biophys. Acta., 611 (1980), 147-). Literature also indicates that both of a cholesterol esterase and a lipase can catalyze the decomposition reaction of triacylglycerol (see W. E. Momsen et al., Biochem. Biophys. Acta., 486 (1977) 103-). At the present time, considerable numbers of enzymes are known which cannot be clearly specified whether a cholesterol esterase or a lipase.
The above-mentioned enzymes are known to be capable of catalyzing the hydrolysis reaction of a carboxylic acid ester in common cases and, on the other hand, also capable of catalyzing the synthetic reaction of an ester.
Lawrence A. et al. indicated that a sterol ester hydrolase derived from canine pancreatic homogenate, which is known as a cholesterol esterase, can catalyze the synthesis of a cholesterol oleic acid ester from free cholesterol and free oleic acid (Biochem. Biophys. Acta., 231 (1971) 558-560). D. Lombardo et al. also indicated that a cholesterol esterase derived from human pancreatic homogenate can catalyze the synthesis of a cholesterol fatty acid ester (Biochimie et al., 1980, 62, 427-432). Myojo et al. confirmed that a lipase can catalyze the synthesis of a cholesterol fatty acid ester (Japanese Patent Application No. 60-45128).
As mentioned above, it has been shown that cholesterol fatty acid esters can be enzymatically synthesized using enzymes.
However, the conventional production processes for cholesterol fatty acid esters with enzymes as mentioned above have the following problems.
(i) All of the above synthesis examples only make mention of the production of sterol fatty acid esters, and are not intended for the production of sterol fatty acid esters for use as daily food materials, health food materials or pharmaceutical materials. In other words, with respect to the reaction conditions and the subsequent purification process, consideration is not given for achieving good flavor qualities (e.g., color, odor and taste) and safety of the sterol fatty acid esters, which are important factors for daily food materials, health food materials and pharmaceutical materials.
(ii) In the above-mentioned synthesis reactions, a highly purified sterol is used as the starting material for the production of a sterol fatty acid ester. Accordingly, the sterol fatty acid ester produced will inevitably become expensive, which is disadvantage in the application to food products from a cost effectiveness viewpoint.
(iii) A vegetable oil deodorizer distillate produced in the deodorization process for a vegetable oil is rich in unsaponifiable matters (including sterols) and fatty acids. Using the vegetable oil deodorizer distillate as the starting material, a sterol fatty acid ester could be produced at low cost. However, it is known that the vegetable oil deodorizer distillate may also contain undesirable components such as peroxides and trans fatty acids resulting from deterioration of fatty acids. The trans fatty acids are known to be mostly produced in a partial hydrogenation process or a deodorization process under high temperature conditions of a fat and oil. Research indicates that intake of a large amount of trans fatty acids by human increases the risk of developing coronary heart disease. Because of public concern about the trans fatty acid content in various food products particularly in Europe and America, many food products containing reduced amounts of trans fatty acids (e.g., margarine) have recently been developed. Therefore, if a sterol fatty acid ester is synthesized from a vegetable oil deodorizer distillate with an enzymes or chemical catalyst capable of randomly catalyzing the esterification reaction, then the resulting sterol fatty acid ester may contain trans fatty acids or other degraded fatty acids, which is undesirable from a safety viewpoint.
Accordingly, the object of the first aspect of the present invention is to provide a process for enzymatically producing a physiologically active dietary sterol fatty acid ester from an inexpensive vegetable oil deodorizer distillate using a lipolytic enzyme (e.g., a lipase) at low cost, in which the reaction conditions for synthesis and subsequent purification process of the sterol fatty acid ester are devised so that the resulting sterol fatty acid ester can be superior in flavor properties (e.g., color, odor and taste) and safety and can be used as a daily food material, a health food material or a pharmaceutical material.
The object of the second aspect of the present invention is to provide a process for producing a dietary sterol fatty acid ester suitable for food and containing no or little deteriorated fatty acids including trans fatty acids, at low cost.
The object of the third aspect of the present invention is to provide a process for producing a dietary sterol fatty acid ester suitable for food and containing no or little trans fatty acids at low cost.